Your email is controlled by a service called BIS ( Blackberry Internet Service)unless you have a corporate server called BES( Blackberry Enterprise Service). My guess is you are having trouble because the old email address is still configured on the carriers BIS site and you need to access that and change the email information. You will need the password used to set up the original configuration. Contact the carrier for information on how to access their system.
This is the link for Rogers https://bis.na.blackberry.com/html?brand=rogers